This project is attempting to determine whether caloric modification of the diets of Rhesus and squirrel monkeys can affect aging rate as assessed by various physiological, biochemical and behavioral indices. Although it has been known for 60 years that reduced feeding extends lifespan, delays and reduces age-related diseases and slows overall aging rate in rodents and lower animals, relevance to primates (especially humans) has never been established. We are examining a battery of indices of aging, as well as acute metabolic effects, of caloric restriction in order to finally answer this question.